What initial screening test is recommended for fetal aneuploidy in the first trimester?

The initial screening test recommended for fetal aneuploidy in the first trimester is the measurement of pregnancy-associated plasma protein A (PAPP-A), beta-human chorionic gonadotropin (beta-hCG), and an ultrasound to assess nuchal translucency. This combination is part of the first-trimester screening and is well-established for evaluating the risk of conditions such as Down syndrome (trisomy 21) and other aneuploidies.

PAPP-A is a placental protein that tends to be lower in pregnancies affected by aneuploidies. Similarly, levels of beta-hCG can be altered in these conditions, aiding in identifying pregnancies at risk for chromosomal abnormalities. The nuchal translucency ultrasound measures the thickness of the fluid at the back of the fetus's neck. Increased thickness can be associated with an increased risk of chromosomal disorders.

This screening is non-invasive and offers valuable information about the likelihood of aneuploidy early in the pregnancy. Its integration of biochemical markers and imaging results makes it an effective initial strategy for assessing fetal risk factors during the critical early stages of gestation.

Other options, such as amniocentesis, are diagnostic procedures that involve sampling amniotic